Dengue Rapid Tests
Dengue virus is a flavivirus, transmitted by tiger mosquitos Aedes aegypti and Aedes albopictus. It is widely distributed throughout the tropical and subtropical areas of the world and causes up to 100 million infections annually. Classic Dengue infection is characterised by a sudden onset of fever, intense headache, myalgia, arthralgia and a rash. Primary dengue infection causes IgM to increase to a detectable level in 3 to 5 days after the onset of fever. IgM generally persist for 30 to 90 days.mMost dengue patients in endemic regions have secondary infections, resulting in high levels of specific IgG prior to or simultaneous with IgM response.
Therefore, the detection of specific anti-dengue IgM and IgG can also help to distinguish between primary and secondary infections. NS1 is one of 7 Dengue virus non-structural proteins which are thought to be involved in viral replication. NS1 exists as a monomer in its immature form, but is rapidly processed in the endoplasmic reticulum to form a stable dimer. A small amount of NS1 remains associated with intracellular organelles where it is thought to be involved in viral replication. The rest of NS1 is found either to be associated with the plasma membrane or to be secreted as a soluble hexadimer. NS1 is essential for viral viability but its precise biological function is unknown. Antibodies produced in response to NS1 in viral infection can cross-react with cell surface antigens on epithelial cells and platelets. This has implications in the development of dengue hemorrhagic fever.
The Dengue NS1 Ag + IgG/IgM Test is a rapid test that utilises a combination of coated dengue antibodies bound to coloured particles for the detection of dengue NS1 antigens and dengue antigens bound to coloured particles for the detection of anti-dengue IgG and anti-dengue IgM in human whole blood, serum or plasma.
The Dengue NS1 Ag + IgG/IgM Test is a qualitative membrane-based immunoassay for the detection of anti- dengue antibodies and dengue NS1 antigens in human whole blood, serum or plasma. The Dengue NS1 Ag + IgG/IgM Test contains two test strips (left side: Dengue NS1 Ag Test; right side: Dengue IgG/IgM Test). The Dengue IgG/IgM Test on the right side consists of two components. In the IgG component anti-human-IgG are precoated in the testline region ‘IgG’. During testing, the specimen reacts with dengue antigen-coated particles in the test cassette. The mixture then migrates along the membrane chromatographically by capillary action and reacts with the anti-human IgG antibodies in the test line region ‘IgG’. If the specimen contains anti-dengue IgG, a coloured line appears in the test line region ‘IgG’. In the IgM component, anti-human IgM antibodies are precoated in the test line region ‘IgM’. If anti-dengue IgM are present in the specimen, they react with the dengue antigen- coated particles in the test cassette. The complex is then captured by the anti-human IgM antibodies, forming a coloured line in the test line region ‘IgM’. If the specimen does not contain dengue antibodies, no coloured line appears in either of the test line regions, indicating a negative result. The Dengue NS1 Ag Test on the left side: During testing, the specimen reacts with dengue antibody-
conjugates on the membrane of the internal test strip. The gold-antibody conjugates bind to dengue antigens in the specimen, which in turn are bound by anti-dengue NS1 antibodies precoated on the membrane. As the mixture moves along the membrane, the anti-dengue NS1 antibodies bind to the antibody-antigen complex, causing pale or dark pink line to form in the test line region ‘NS1’ of the membrane. The colour intensity of the lines may vary depending upon the amount of antigens present in the sample. The appearance of a pink line in the test line region ‘NS1’ should be considered as a positive result. If the specimen does not contain dengue antigens, no coloured line appears in the test line region, indicating a negative result. The appearance of both coloured lines in the control line regions (C) serve as a procedural control, indicating that proper volume of specimen has been added and membrane wicking has occurred.
